1. Field of the Invention
The present invention relates to a graph display apparatus for inputting a functional formula or the like, calculating the graph of the input functional formula or the like, and displaying the calculated graph and, more particularly, to a graph display apparatus which can display the graphs of a functional formula obtained by changing coefficients of the functional formula.
2. Description of the Related Art
Electronic calculators which have a functional calculation function and which also have a graph display function for calculating and displaying the graph of an input functional formula have been commercially available.
More specifically, a functional formula to be displayed is input in advance, and X-coordinate values in units of display dots on a dot-matrix display apparatus are also substituted in the input functional formula by inputting X- and Y-coordinate ranges (Xmin, Xmax) and (Ymin, Ymax) of the functional formula. With this operation, calculated Y-coordinate values are sequentially written on a VRAM (video memory), thus displaying the graph of the functional formula. Such a graph display technique is described in, e.g., U.S. Pat. No. 4,794,553, U.S. Pat. No. 4,794,554, and the like. Therefore, in the conventional graph display apparatus, both a functional formula to be displayed and X- and Y-coordinate ranges must be input with keys, resulting in very cumbersome operations.